1. Field of the Invention
The present invention generally relates to battery terminal connectors which are employed to connect a wire harness or electrical cable to a battery in automotive and marine applications. More specifically, this invention pertains to a two-piece stamped battery terminal connector whose construction provides improved retention of the connector to the battery post while also permitting repeated use without significant loss in structural integrity.
2. Description of the Prior Art
Electrical harnesses and battery cables used in automotive and marine applications are typically attached to the terminal post of a lead-acid storage battery with some form of battery terminal connector. To ensure that a reliable electrical contact is maintained, the battery terminal connector must be constructed such that it will remain securely attached to the terminal post of the battery even when subjected to road vibrations and various other adverse conditions. At the same time, the battery terminal connector must almost permit the battery cable to be easily disconnected and reconnected from the battery to facilitate the removal or replacement of the battery. As a result, the structural criteria for battery terminal connectors includes the retention strength of the connector, the ease with which the connector can be attached to and detached from the battery, and the ability to be reused numerous times without a significant loss in the structural integrity of the connector.
Conventionally, a battery terminal connector is attached to one of two battery terminal posts which are formed from a lead alloy. Typically, the terminal post has the shape of an inverted frustum of a cone, which facilitates the ease by which the connector can be mounted to and removed from the terminal post. The most common form for a battery terminal connector is a die cast lead split collar design. The collar includes a yoke formed at the split to form a slot therebetween. The split collar construction enables the connector to be expanded and easily slipped over the battery terminal post. Thereafter the slot is collapsed, generally with a bolt and nut combination mounted to the yoke, to reduce the diameter of the collar and thereby frictionally secure the connector to the battery post.
However, the smooth tapered shape of the terminal post does not provide an ideal attachment site for the connector. In particular, the shape of the terminal post naturally urges the connector upward and off the terminal post when subjected to vibration or accidental impact. This condition is further exasperated by the use of petroleum jelly or other lubricants which are often applied to the terminal post to reduce the buildup of chemical deposits on the terminal post and connector. As a result, a very high clamping force is necessary to provide reliable attachment of the connector to the terminal post.
However, conventional connectors have a smooth and equally-tapered interior surface by which contact is made with the terminal post. As a consequence, the clamping pressure of the connector is reduced because it is distributed over the relatively large and uninterrupted surface of the terminal post. Such connectors must therefore be designed to have sufficient structural strength to impart higher clamping forces on the terminal post than would be required if either the connector or the terminal post were provided with an irregular surface feature.
To reduce the level of clamping loads necessary to retain the connector on the terminal post, it has been suggested in the prior art to provide longitudinal serrations or the like about the circumference of the connector. Examples include U.S. Pat. No. 2,068,452 to Hansen, U.S. Pat. No. 4,063,794 to Dittmann, and U.S. Pat. No. 4,354,726 to Kato et al. While such an approach does improve the clamping pressure of the connector relative to its available clamping load by reducing the connector's contact area, the slight twisting action often necessary to remove a connector from the terminal post will severely damage the soft lead material from which the terminal post is made.
Even when a connector is adequate in terms of gripping power, repeated detaching and reattaching of the connector causes work hardening and plastic deformation of the material, thereby making it more difficult to sufficiently clamp the connector onto the post to get an adequate electrical connection. Consequently, as the clamping force of the connector is reduced, it becomes prone to being vibrated or accidently dislodged from the battery post. In automotive and marine applications, the resulting loss of electrical power to the vehicle's accessories, such as headlamps and control systems, can be extremely hazardous.
While die cast lead connectors are more common, one-piece battery terminal connectors formed from sheet metal have been suggested by the prior art due to the manufacturing advantages associated with shearing, stamping and bending operations, such as lower costs and reduced waste and scrappage. Examples of stamped connectors known in the prior art are taught by U.S. Pat. No. 2,222,577 to Thompson, U.S. Pat. No. 3,568,138 to Bakker et al., and U.S. Pat. No. 4,054,355 to Kourimsky et al. While each of the approaches taught by the above prior art provides manufacturing benefits, each is generally limited in terms of the clamping force it can generate and/or its structural strength. Because of the substantially unreinforced framework formed during the bending operation, the connectors of both Thompson and Bakker are highly susceptible to plastic deformation and buckling of the connector under high clamping loads, particularly at the point where the fastener passes through the connector. The connector taught by Kourimsky is susceptible to plastic elongation of the clamping arms because, with three clamping bands and the limited length of the terminal post, the widths of the bands are severely limited. Moreover, the connector taught by Bakker is highly susceptible to work hardening and fracture of the connector material from repeated use because the connector's arms are flexed in the plane corresponding to their widest dimensions, which intensifies the elongation and compression at the connector's radially outer-and inner-most extremities, respectively. Accordingly, the stamped battery terminal connectors of the prior art do not provide adequate strength and structural durability to survive the repeated use and abuse often encountered in automotive and marine applications.
From the above discussion, it can be readily appreciated that the prior art does not disclose a battery terminal connector which has the cost advantages of being formed by a stamping operation while also providing the structural and clamping strength necessary to survive repeated use in an automotive or marine environment.
Accordingly, what is needed is a low-cost battery terminal connector which can be formed by a stamping operation, while being capable of providing sufficient structural strength and flexibility to permit repeated attachment and detachment. In addition, such a terminal connector should also possess the ability to generate a clamping force which will securely retain the connector on the battery terminal post without damaging the terminal post.